In-situ observation of damage evolution and fracture in AlSi7Mg0.3 cast alloys

The mechanisms which occur during damage initiation, evolution and crack growth in AlSi7Mg0.3 cast alloys are studied by in-situ tensile testing in a scanning electron microscope. It is shown that microcracks in these alloys are predominantly formed in the Si particles. Shear bands are seen to precede the breaking of the Si particles and the dislocation pile-up mechanism can thus be con®rmed as the dominant damage initiating process in the matrix. Both microand macrocrack coalescence have been observed in the course of the experiments. The e€ect of the microstructure of the AlSi7Mg cast alloys on damage nucleation, crack formation and compliance reduction is analysed. # 1999 Elsevier Science Ltd. All rights reserved.